A little change on wording for new-user email

adds missing wording missed in https://github.com/gitlabhq/gitlabhq/commit/58d6176bc35fb45427df75b9762df6bb0d3b3a98 and https://github.com/gitlabhq/gitlabhq/pull/3902
Merge pull request #3961 from bbodenmiller/patch-1

A little change on wording for new-user email